Sludge treatment



March 31, 1942. D, SANDERS SLUDGIE TREATMENT Filed Nov. 9, 1936 A rrcsrPatented Mar. 31, .1942 g UNITED STATES PATENT OFFICE SLUDGE TREATMENTMarion D. Sanders, Chicago, Ill., assignor to Industrial PatentsCorporation, Chicago, Ill., a i I i corporation of Delaware ApplicationNovember 9, 1936, Serial No. 110,008

11 Claims.

This invention relates to the treatment of sludge and to the productthereof.

One of the objects of the invention is to provide a method for thetreatment of sludge derived from packing house wastes.

Another object of the invention is to provide a new product of value asan animal food.

Another object of the invention is toprovide an organic substance ofvalue in soil fertilization.

Figure 2 is a plan view of the layout shown in Figurev 1. I

Sludge derived, for example, from packing house wastes stored in sludgepit I may be passed Another object of the invention is to provide thesludge pit to the cooker. a novel product high in protein value. Sludgerec v f packing h se Wa s Another object of the invention is to providein accordance with the method described in my an economical andefiective method for dewatercopending app a af r said h s a s lidsconing sludges of high protein content. tent of approximately 3 to 6 percent.

Other objects of the invention willbe'apparent A a t y Procedure y p y a1500 from the description and claims which follow. 1 gallon sludgecooker. A er e Sl d o r is In my copending application entitled Leatfillwith sludge, heat is applied to coa e ment of wastes, Serial No.110,007, filed Novemthe Proteins in the Sludge, causing the m j r her 9,1936, which has matured into United State portion of solids to separatefrom the water in a Patent No. 2,204,703, I have described and mannerwhich will hereinafter be more particuclaimed an improved method fortreating wastes r y e ib e eoagulated Sludge y then suclti atsegacidnghouse gwasteis, by which a con- 2e remogeg fr i i i the sl i o k r t h pg cen ra suspension 0 pro eins is flocculated D 8 W1 a Ve ryi o e frompacking house wastes by the addition of a Process With the eq p e showin e drawmineral acid and a protein coagulant. As will n the Sludge is prmit ed to ferment in the be apparent from the specification, theprocess Sludge pi i the Sludge w f r a P ri d of therein describedinvolves conditioning the prof ts s d yg ga g at Fgeh pe ature o tein inpacking house wastes rich in protein, and m eg ees egrees ienheit aftersubstantially dewatering the conditioned protein. Which I have found hthe effect of the h l Various methods have been employed from S sludge:3! 15 Qause the coagulated time to time in the treatment of sewage, theob- S ge 0 form a semisolid mass Scum j ct of n such methods being todevelop a re1a at the topzotf) the cooker-,thaving a solids content 1tlvely innocuous efliuent by the removal of solids of m 1 P therefrom inthe f f' d The primary After coagulation in this manner, therelativelyobjects of sewage treatment methods being relawater beneath Pi ted sludge 1S- tive purification of the water or eiiiuent the wlthdmwnz ga mm 8 pmvlded Wlth Valve The concen ra e s udge is removed throughpipe zlliidge has constituted a major problem in the 6, as has beenpointed out and dehydrated y te means sufliciently to form a Sludge fromsome types of sewage has been any a'ppmpna used to a Small extent toprovide Organic ingredi 40 granular, compact, sohd material which isrelant f f r i tur b t rdinar sludge tively high m protein. t ro; szwage treatment l jits has little ezonomic Any desired means may beemployed for heat 1 fie P d t th v mg the sludge as direct steaminjection through and 9 expense 8 inlet III provided with valve u. Ventpipe I2 is necessity of some disposition. Insome large provided in cover'3 secured by lugs P 5 15? the sludgeis filtered and incinerated, I havefound that heat is an effective means stituitmg amajor item of expenseof sewage trea for facilitating dewatering of the sludge. If the men rawsludge is heated without conditioning by The Present invehtmnlsdll'ectedfio shldge P fermentation, the efiect of the heat is to formduced by the f fh wastes mgh m pmtem' arge discrete particles dispersedthroughout the In the drawin s ar cte o reference liquid, which may bereadily removed by known in the several indicate similarpa tsfiltrat onmethods. According to one aspect of Fiui'gure g. ismahside vigw, partlyan SCt10ll, 0; Lliiehpresent invention, tdllierefore,f the raw-sludge PW 6 y e P Y m carrym g in pro ein is con ioned' or filtration by out theprocess of the present invention. the application of heat in any desiredmanner per hour for each square foot of filter area.

although direct steam injection is the most efiicient method. Thetemperature of the raw sludge is raised to a point above 150 degreesFahrenheit, preferably to a temperature of from about 180 degrees to 200degrees Fahrenheit, at which the phenomenon of the formation of largediscrete particles reaches its optimum.

As is well known, it is usual in the employment of vacuum filters fordewatering sludge to accumulate about one pound of dry solid per squarefoot of filter area per hour although I have found in practice that withraw sludge derived from packing house wastes but one-half pound of drysolids per square foot of filter area may be accumulated per hour with avacuum filter.

I have found that heating raw sludge derived from packing house wastesat the temperatures indicated for a period of five minutes permits theaccumulation of four pounds of dry solids The eflieiency of filtrationis not materially afiected by the temperature of the liquid at the timeof filtration.

It will be readily appreciated that the present invention, whichinvolves the heating of slugs to facilitate dewatering, greatlyincreases the efiiciency of known dewatering procedures.

Examples of tests'of the heat coagulation of sludge from chemicallyprecipitated packing house wastes are given in the following table whichgives the analyses of the coagulated or substantially dewatered sludgecollected in a supernatant layer in the sludge cooker. The sludgetreated in both tests was fermented twenty-four hours at 70 degreesFahrenheit and then heated to 180 degreesFahrenheit by the directinjection'of steam.

The preferred procedure in carrying out the present invention on packinghouse wastes or liquids highin protein values involves the preliminaryfermentation of the sludge, which has already been described. Thisfermentation is in no sense a digestion for the purpose of destroyingvolatile matter, and the fermentation is not carried to anythingapproaching substantial digestion of volatile matter. The material ispermitted to remain at a temperature of approximately 65 degrees to 110degrees Fahrenheit for a period of twenty-four hours, which issuflicient to develop some gasin the liquid before the application ofheat and the consequent coagulation of the proteins. The gas thus formedeffectively carries the coagulated material to the top of the vessel,forming a layer of semi-solids or scum, which has already beendiscussed. The substantially dewatered sludge thus obtained is removedfrom the cooker and further dried. In practice, I have successfullydried this dewatered sludge containing about 12 per cent solids by firstconcentrating to about 60 percent solids in a hydraulic press andthenfurther drying the cakes thus produced to an end product having 90per cent solids. A conventional rotary or other drier may be used inthis procedure.

Another efiective procedure for preparing the relatively dry end productdesired involves the employment of a steam'jacketed drying kettleequipped with stirrers having a forced draft in the kettle to carry awaythe evaporated moisture. It will be readily understood that anyevaporator or drier may be employed to roduce a relatively dry endproduct, consideration being had for the purpose to which it is desiredto put the end product. The end product which results from the treatmentof normal packing house wastes in accordance with the present inventionwill vary in analysis depending upon the operations of the packinghouse. The character of the end product will be readily understood byreference to the following table:

Per cent Per cent 4. 40 6.

have

Sample A in the foregoing table was produced from a packing house wastesecured from a grease skimming basin which was relatively inefficient.

Sample B was produced from packing house waste which had beenefiiciently degreased and contained in the original state aproximately100 parts per million of fat.

In addition to protein, fat, and moisture, the end product contains someinert substances and small quantities of calcium phosphate, ferricoxide, and other minerals.

Depending upon market conditions for inedible greases, the high greasecontent which appears in the foregoing sludge cake as shown in theforegoing table may be economically reduced'to about 10 per cent and theprotein percentage correspondingly raised by hot-pressing thesubstantially dewatered sludge in a hydraulic press or extracting thefat with appropriate solvents. The dried sludge cake constitutes a newproduct high in food value comparable in characteristics to digestertankage, which is an important in- Y gredient of animal feed used inswine and other livestock feeding.

.In preparing the sludge cake of the present invention for use in animalfeeds, it is merely necessary to grind it, whereupon it is in conditionfor, packaging and shipment or immediate used.

The term "sludge is used in the foregoing specification in threedistinct senses, which will be readily understood from the context.

In the first place, it is used in the usual accepted sense as referringto the liquid layer relatively high in solids which accumulates at thebpttom of a settling tank in conventional sewage treatment methods andwhich is removed from the settling tank in accordance with the proceduredescribed and claimed in my copending application entitled Treatment ofwastes, Serial No. 110,007 which matured into Patent No. 2,204,703, June18, 1940.

In the second place, the term "sludge in this specification is appliedto the raw sludge which has been heated without preliminaryfermentation. This coagulated sludge does not difier from raw sludge insolids content, but does differ from raw sludge in its physicalcharacteristics, particularly in filterability.

In the third place, the term "sludge" is applied to the substantiallydewatered sludge found as an upper layer in the sludge cooker after theheat treatment of preliminarily fermented raw sludge.

In addition to these meanings of the term sludge, the term is employedin a modifying sense indicative of. source to the dried end product. Theterm sludge" must be understood to be broad enough to include materialrecovered from wastes, which material has a higher solids .content thanthe waste from which it is reing the sludge sufliciently to form gastherein, heating the sludge to a temperature above 150 degreesFahrenheit to coagulate the proteins in the sludge, collecting asubstantially dewatered sludge in a supernatant layer, and thereafterdrying the substantially dewatered sludge.

4. .The method of treating sludge derived .from packing house wasteswhich comprises fermenting the sludge sufllciently to form gas therein,heating the sludge to a temperature of from 180 degrees to 200 degreesFahrenheit to coagulate the proteins in'the sludge, collecting asubstantially dewatered sludge in a supematant'layer, and thereafterdrying the substantially dewatered sludge.

degrees to 200 degrees Fahrenheit to coagulate the proteins, andfloating the coagulated proteins with the gas formed inthe sludge.

"l. The method of concentrating chemically precipitated packing housewastes which comprises fermenting the chemically precipitated wastessufiiciently to form gas therein, but insufliciently to substantiallydigest the chemically precipitated wastes, and then heating thetermented wastes to form a substantially dewatered chemicallyprecipitated waste.

8. The method of recovering proteins from chemically precipitatedpacking house wastes containing proteins which comprises fermenting thechemically precipitated wastes sufiiciently to form gas therein, formingdiscrete particles in the chemically precipitated wastes by heating thechemically precipitated packing house wastes to a temperature above 150degrees Fahrenheit, and thereafter recovering the discrete particlesfrom the chemically precipitated wastes.

9. The method of recovering solids from chemically precipitated packinghouse wastes which comprises fermenting the chemically precipitated 5.The method of recovering solids from sludge derived from packing housewastes which comprises fermenting the sludge sufliciently to form wastessufliciently to form gas therein, forming discrete particles by heatingthe chemically precipitated wastes to a temperature of from degrees to200 degreesFahrenheit, floating the discrete particles with the gasformed inthe chemically precipitated wastes, and thereafterrecoveringthe discrete particles from the chemically precipitated wastes.

10. The method of treating chemically pre- I cipitated packing housewastes containing proteins which comprises fermenting the chemicallyprecipitated wastes s'ufliciently to form gas therein, coagulating theproteins by heating the chemically precipitated wastes to a temperatureof wastes which comprises fermenting the chemically precipitated wastessuflieiently to form gas therein, heating the fermented product tocoagulate the proteins, floating the coagulated product with the gasformed in the fermentation and recovering the floated material.

MARION n.

